The invention relates to a method of manufacturing mouldings from powder material wherein the powder material is filled into preformed capsules, which are thereafter evacuated and gas-tightly sealed before being compacted into essentially dense bodies by isostatic pressing. The invention is especially applicable to the manufacture of mouldings with small individual weights or in large series.
When compacting powder material by means of isostatic pressing, the powder material is enclosed in a deformable, gas-tight capsule before the isostatic pressure is applied to the body from a surrounding pressure medium.
The body is formed, for example by filling powder into a preformed capsule, but the powder may also be preformed into a green body from which binder (if any) is driven off before the body is coated with a dense, encapsulating layer.
In the manufacture of metallic bodies by isostatic pressing, the metal powder is usally filled into a preformed thin sheet capsule. The costs of manufacturing the sheet metal capsule limits the application of isostatic pressing since the relative importance of the mould costs for the total cost of the mouldings increases with decreased individual weight, with reduced alloying content, and with an increasingly complex shape, but remains essentially unaffected by the length of the series. The cost picture which arises when each moulding requires a seal-welded and pressure-tested capsule restricts the possibilities of using isostatic pressing, especially when manufacturing mouldings with small individual weights, a complex shape, or low material costs.